<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width: 200px;height: 200px;
      border: 10px inset red;
      /*设置圆角:值越大越圆,超过宽高的一半时为正圆*/
      border-radius: 200px;
    }
    #d2{
      width:300px;
      height: 300px;
      border:1px solid blue;
      /*默认情况下给元素添加内边距会影响元素的宽高*/
      padding-top: 100px;
      padding-left: 100px;
      /*添加此样式后内边距将不再影响元素的宽高*/
      box-sizing: border-box;

    }
  </style>
</head>
<body>
<div id="d1">边框测试</div>
<div id="d2">内边距测试</div>
</body>
</html>